U.S. patent application number 12/096038 was filed with the patent office on 2009-12-17 for method for manufacture of dome cover, dome cover, and dome-type camera.
This patent application is currently assigned to MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.. Invention is credited to Gentarou Irisawa, Noboru Takada.
Application Number | 20090310956 12/096038 |
Document ID | / |
Family ID | 38162947 |
Filed Date | 2009-12-17 |
United States Patent
Application |
20090310956 |
Kind Code |
A1 |
Takada; Noboru ; et
al. |
December 17, 2009 |
METHOD FOR MANUFACTURE OF DOME COVER, DOME COVER, AND DOME-TYPE
CAMERA
Abstract
A dome cover (6) is manufactured by injection molding by steps
of: forming a cavity (14) having the shape of the dome cover (6)
between an upper mold (12) and a lower mold (13) for an injection
molding die (11), providing a gate port (16) for injecting melt
resin at a position (of the upper mold (12)) corresponding to the
zenithal portion (15) of the dome cover (6), and injecting the melt
resin into the cavity (14) through the gate port (16). The resin
injected from the center portion (the portion corresponding to the
zenithal portion (15) of the dome cover (6)) of the cavity (14)
flows uniformly toward the circumference of the cavity (14).
Therefore, variations in pressure and temperature of the resin in
the cavity (14) are restrained and, consequently, molding
irregularity of the manufactured dome cover (6) is restrained.
According to the method of manufacturing the dome cover as
described above, generation of the partial molding irregularity on
the manufactured dome cover is restrained.
Inventors: |
Takada; Noboru; (Kanagawa,
JP) ; Irisawa; Gentarou; (Kanagawa, JP) |
Correspondence
Address: |
PEARNE & GORDON LLP
1801 EAST 9TH STREET, SUITE 1200
CLEVELAND
OH
44114-3108
US
|
Assignee: |
MATSUSHITA ELECTRIC INDUSTRIAL CO.,
LTD.
Osaka
JP
|
Family ID: |
38162947 |
Appl. No.: |
12/096038 |
Filed: |
December 13, 2006 |
PCT Filed: |
December 13, 2006 |
PCT NO: |
PCT/JP2006/324837 |
371 Date: |
June 4, 2008 |
Current U.S.
Class: |
396/427 ;
264/250; 428/35.7 |
Current CPC
Class: |
B29C 45/2708 20130101;
Y10T 428/1352 20150115; B29C 45/0025 20130101; G03B 15/00 20130101;
B29C 2045/0027 20130101 |
Class at
Publication: |
396/427 ;
264/250; 428/35.7 |
International
Class: |
G03B 17/02 20060101
G03B017/02; B29C 45/14 20060101 B29C045/14; B29D 25/00 20060101
B29D025/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 14, 2005 |
JP |
2005-360508 |
Claims
1-6. (canceled)
7. A method of manufacturing a dome cover comprising: forming a
cavity which has a shape of the dome cover between a first metal
mold and a second metal mold for injection molding; providing a
gate port for injecting melt resin at a position of the first metal
mold corresponding to a zenithal portion of the dome cover;
injecting the melt resin into the cavity through the gate port to
manufacture the dome cover by injection molding; using a secondary
processing apparatus which has a mirror-finished contact surface,
and pressing the contact surface to the zenithal portion of the
dome cover manufactured by injection molding; welding resin at the
zenithal portion of the dome cover; and transferring the
mirror-like shape of the contact surface of the secondary
processing apparatus to the zenithal portion of the dome cover.
8. The method of manufacturing a dome cover according to claim 7,
comprising: melting resin at the zenithal portion of the dome cover
by ultrasonically vibrating the contact surface of the secondary
processing apparatus.
9. The method of manufacturing a dome cover according to claim 8,
comprising: vibrating the contact surface of the secondary
processing apparatus along a tangential direction at the zenithal
portion of the dome cover.
10. A dome cover manufactured by the method of manufacturing a dome
cover according to any one of claims 7-9.
11. A dome-type camera comprising: the dome cover according to
claim 10; and a camera provided inside the dome cover.
12. A dome-type camera comprising: a dome cover which is
manufactured by forming a cavity which has a shape of the dome
cover between a first metal mold and a second metal mold for
injection molding, providing a gate port for injecting melt resin
at a position of the first metal mold corresponding to a zenithal
portion of the dome cover, injecting the melt resin into the cavity
through the gate port to manufacture the dome cover by injection
molding; and a camera provided inside the dome cover.
Description
TECHNICAL FIELD
[0001] The present invention relates to a dome cover used for a
dome-type surveillance camera or the like.
BACKGROUND ART
[0002] Hitherto, a surveillance camera installed on walls or
ceilings of facilities is known. Such surveillance camera includes
a dome cover for containing and protecting a lens. The dome cover
is typically made of transparent resin. The dome cover includes a
semi-spherical dome portion which has an opening and a flange
portion which is provided with the peripheral edge of the opening.
The lens of the surveillance camera rotates in a pan direction or
in a tilt direction in a state of being contained in the dome
cover. Shooting of surveillance video is carried out through the
transparent dome cover. The dome cover is required to have an
optically high performance. For example, the dome cover is required
to have a performance to provide a high-quality, high-resolution
camera image shot therethrough. A dome-type camera as described
above is disclosed in JP-A-2005-300659 (pages 4-6, FIG. 2).
[0003] The dome cover as described above is manufactured, for
example, by injection molding. A cavity which has a shape
corresponding to the shape of the dome cover is formed between an
upper mold and a lower mold of a metal mold used for the injection
molding. The metal mold for injection molding in the prior art has
a gate port for injecting resin at a position corresponding to the
flange portion of the dome cover so as to prevent a gate trace from
being left on the dome portion of the molded dome cover. For
example, the gate port is provided with a lateral side of the
cavity (a circumference of the substantially circular cavity in
plan view). Then, heated and melt resin is injected into the cavity
through the gate port of the injection molding die, and the resin
is cooled and cured. In this manner, the dome cover is manufactured
by the injection molding. Such injection molding die is disclosed,
for example, in JP-A-2003-285351 (pages 3-6, FIG. 2).
[0004] However, according to the method of manufacturing the dome
cover in the prior art, the resin is injected through the gate port
provided with the lateral side of the cavity. Therefore, the resin
injected from the lateral side of the cavity (one of the
circumferences of the substantially circular cavity in plan view)
flows around to the center of the cavity (which corresponds to a
zenithal portion of the dome cover), and then flows toward an exit
portion of the other circumference of the cavity. When the resin
flows in the cavity as described above, the flow of the resin is
not uniform near the gate port and the exit portion, and the
pressure and the temperature of resin in the cavity varies.
Therefore, the dome cover manufactured in the method in the prior
art, molding irregularity occurs at portions corresponding to the
gate port and the exit portion, and hence optical irregularities
(lowering of the quality or the resolution of the camera image) may
occur.
DISCLOSURE OF INVENTION
Problems to be Solved by the Invention
[0005] The present invention is achieved in the background as
descried above. It is an object of the present invention to provide
a method of manufacturing a dome cover in which occurrence of
partially molding irregularity is restrained.
Means for Solving the Problems
[0006] One aspect of the present invention is a method of
manufacturing a dome cover, which comprises: forming a cavity which
has a shape of the dome cover between a first metal mold and a
second metal mold for injection molding; providing a gate port for
injecting melt resin at a position of the first metal mold
corresponding to a zenithal portion of the dome cover; and
injecting the melt resin into the cavity through the gate port to
manufacture the dome cover by injection molding.
[0007] Another aspect of the present invention is a dome cover,
which is manufactured by the method of manufacturing a dome cover
described above.
[0008] Another aspect of the present invention is a dome-type
camera, which comprises: the dome cover described above; and a
camera provided inside the dome cover.
[0009] As described below, there are other aspects of the present
invention. Therefore, disclosure of the invention is intended to
provide some aspects of the present invention, and is not intended
to limit the scope of the invention described and claimed here.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a cross-sectional view of a injection molding die
(in a state in which a gate pin member is pulled out) for a dome
cover in the embodiment of the present invention.
[0011] FIG. 2 is a cross-sectional view of the injection molding
die (in a state in which the gate pin member is inserted) for the
dome cover in the embodiment of the present invention.
[0012] FIG. 3 is a cross-sectional view of the dome cover
manufactured according to the embodiment of the present
invention.
[0013] FIG. 4 is a perspective view of the dome cover manufactured
according to the embodiment of the present invention.
[0014] FIG. 5 is a front view of a dome-type camera according to
the embodiment of the present invention.
[0015] FIG. 6 is a side view showing a state of secondary
processing of the dome cover according to the embodiment of the
present invention.
[0016] FIG. 7 is a perspective view showing a state of secondary
processing of the dome cover according to the embodiment of the
present invention.
[0017] FIG. 8 is an explanatory drawing of a modification of the
dome cover in the embodiment of the present invention.
[0018] FIG. 9 is a side view for describing a state of shooting
with a dome-type camera (the shooting state at the TELE end in the
horizontal direction) in the embodiment of the present
invention.
[0019] FIG. 10 is a side view for describing the state of shooting
with the dome-type camera (the shooting state at the WIDE end in
the right downward direction) in the embodiment of the present
invention.
REFERENCE NUMERALS
[0020] 1 dome-type camera [0021] 6 dome cover [0022] 11 injection
molding die [0023] 12 upper mold (first metal mold) [0024] 13 lower
mold (second metal mold) [0025] 14 cavity [0026] 15 zenithal
portion [0027] 16 gate port [0028] 18 gate pin member [0029] 19
upper mold inner peripheral surface (inner peripheral surface of
the first metal mold) [0030] 20 pin end surface (distal end surface
of the gate pin member) [0031] 21 ultrasonic welder apparatus
(secondary processing apparatus) [0032] 22 horn member [0033] 23
distal projection [0034] 24 lower surface (contact surface) of the
distal projection of the horn member
BEST MODE FOR CARRYING OUT THE INVENTION
[0035] Detailed description of the present invention will be
described below. However, the detailed description and the attached
drawings are not intended to limit the invention. Instead, the
scope of the invention is limited by appended claims.
[0036] A method of manufacturing a dome cover according to the
present invention includes: forming a cavity having a shape of the
dome cover between a first metal mold and a second metal mold for
injection molding; providing a gate port for injecting melt resin
at a position of the first metal mold corresponding to a zenithal
portion of the dome cover; and injecting the melt resin into the
cavity through the gate port to manufacture the dome cover by
injection molding.
[0037] According to this method, the resin injected from the center
portion of the cavity (the portion of the dome cover corresponding
to the zenithal portion) flows uniformly toward the circumference
of the cavity. Therefore, occurrence of variations in pressure or
in temperature of the resin in the cavity is restrained, and hence
molding irregularity of the manufacture is prevented from occurring
on the manufactured dome cover.
[0038] The method of manufacturing the dome cover in the present
invention may include: using a secondary processing apparatus
having a mirror-finished contact surface, and pressing the contact
surface to the zenithal portion of the dome cover manufactured by
injection molding; welding resin at the zenithal portion of the
dome cover; and transferring the mirror-like shape of the contact
surface of the secondary processing apparatus to the zenithal
portion of the dome cover.
[0039] The secondary processing can be applied to the zenithal
portion of the dome cover by transferring the shape of the
mirror-finished contact surface of the secondary processing
apparatus to the zenithal portion of the dome cover. For example,
if a trace of the gate port (gate trace) is left at the zenithal
portion of the dome cover, the gate trace can be shaded out easily
by the secondary processing.
[0040] The method of manufacturing the dome cover according to the
present invention may include melting resin at the zenithal portion
of the dome cover by ultrasonically vibrating the contact surface
of the secondary processing apparatus.
[0041] In this method, the resin at the surface of the zenithal
portion of the dome cover melts while ultrasonic vibrations are
being applied. Therefore, in comparison with the case in which
resin is heated and melted, the degree of melt of the resin can be
easily controlled. When the ultrasonic vibrations are stopped, the
resin at the zenithal portion of the dome cover is cooled and
cured. Therefore, the time required for curing the resin can be
short, and hence the time required for the secondary processing can
be reduced.
[0042] The method of manufacturing the dome cover according to the
present invention may include vibrating the contact surface of the
secondary processing apparatus along a tangential direction at the
zenithal portion of the dome cover.
[0043] In this method, the resin at the zenithal portion of the
dome cover is easily melted by friction generated between the
ultrasonically vibrating contact surface and the zenithal portion
of the dome cover.
[0044] The method of manufacturing the dome cover according to the
present invention, wherein a gate pin member which is removably
inserted into the gate port is provided, may include: pulling out
the gate pin member to a pulled-position to open the gate port when
the resin is injected; and inserting the gate pin member to an
inserted-position to close the gate port with the gate pin member,
and forming a continuous surface with an inner surface of the first
metal mold around the gate port and a distal end surface of the
gate pin member after the resin has injected.
[0045] In this method, since the gate port positioned at the
zenithal portion of the dome cover is closed by the gate pin member
and the continuous surface is formed by the distal end surface of
the gate pin member after the resin has injected, the gate trace at
the zenithal portion of the dome cover can be made smaller.
[0046] The dome cover according to the present invention comprises
the dome cover manufactured by the manufacturing method described
above.
[0047] The dome-type camera according to the present invention
comprises the dome cover described above and a camera provided
inside the dome cover.
[0048] In the present invention, by injecting melt resin in the
cavity through the gate port provided at the position corresponding
to the zenithal portion of the dome cover, it can be prevented to
generate the partial molding irregularity on the manufactured dome
cover.
[0049] Referring now to the drawings, a method of manufacturing the
dome cover according to the embodiment of the present invention
will be described. In this embodiment, a case of manufacturing the
dome cover to be used for a dome-type surveillance camera installed
on a ceiling or the like of a facility by injection molding will be
exemplified.
[0050] An injection molding die for a dome cover according to the
embodiment of the present invention will be shown in FIG. 1 and
FIG. 2. FIG. 1 and FIG. 2 are cross-sectional views of the
injection molding die viewed from the side. FIG. 3 is a
cross-sectional view of the dome cover manufactured by injection
molding viewed from the side. FIG. 4 is a perspective view of a
dome cover. FIG. 5 is a front view of a dome-type camera provided
with the dome cover.
[0051] Referring now to FIG. 3 to FIG. 5, configurations of the
dome-type camera and the dome cover will be described.
[0052] As shown in FIG. 5, a dome-type camera 1 includes a main
body 3 having a mounting member 2, a lens 5 of a surveillance
camera 4 provided with the lower portion of the main body 3 and a
dome cover 6 for containing and protecting the lens 5. The
dome-type camera 1 is attached, for example, to a ceiling or the
like of a facility by the mounting member 2.
[0053] The main body 3 is provided with a pan-tilt mechanism 7 for
turning the lens 5 of the surveillance camera 4 in the pan
direction (horizontal direction) and the tilt direction (vertical
direction). Although it is not specifically shown, the lens 5
includes a plurality of lenses assembled in a lens-barrel. An image
sensing device such as CCD is built in the back of the barrel. The
surveillance camera 4 is configured in this manner.
[0054] The dome cover 6 is attached to the main body 3 in a state
of containing the lens 5. As shown in FIG. 3 and FIG. 4, the dome
cover 6 includes a substantially semi-spherical dome portion 9
having an opening 8 and a flange portion 10 provided so as to
protrude outward from the peripheral edge of the opening 8. In FIG.
3 and FIG. 4, the dome cover 6 having the dome portion 9 of a shape
combining a semi-sphere and a cylinder is illustrated as an
example. However, the cylindrical portion of the dome portion 9
does not necessarily have to be provided, and the dome portion 9 of
the dome cover 6 may be formed into a semi-spherical shape. In FIG.
1 and FIG. 2 described later, illustration of the cylindrical
portion of the substantially semi-spherical dome cover 6 is omitted
for the sake of simplification of description.
[0055] As shown in FIG. 5, in this embodiment, the optical axis of
the lens 5 is offset from the center of the semi-sphere of the dome
cover 6 toward the zenith of the dome cover 6 in a state in which
the lens 5 is directed in the horizontal direction (see FIG. 8).
With this offset, the lens 5 is able to shoot the front without
being disturbed by the main body 3 (without obstructing the angle
of view of the camera by the main body 3) when the lens 5 is
directed in the horizontal direction.
[0056] The dome cover 6 is made of transparent resin. In this
embodiment, transparent synthetic resins such as polycarbonate
(PC), acryl, or acrylonitrile butadiene styrene (ABS) are used as
the material of the dome cover 6. The dome cover 6 is required to
have an optically high performance. For example, the dome cover 6
is required to have a performance to provide a high-quality,
high-resolution camera image shot therethrough.
[0057] Referring now to FIG. 1 and FIG. 2, a configuration of a
molding die 11 used for manufacturing the dome cover 6 by injection
molding will be described.
[0058] As shown in FIG. 1 and FIG. 2, the injection molding die 11
is provided with an upper mold 12 and a lower mold 13 which are
opened and closed upward and downward. A cavity 14 of a
substantially semi-spherical shape which corresponds to the shape
of the dome cover 6 is formed between the upper mold 12 and the
lower mold 13. The upper mold 12 is provided with a gate port 16
for injecting melted resin at a position corresponding to a
zenithal portion 15 (topmost portion) of the dome cover 6. The
upper mold 12 is also provided with a cooling medium flow channel
17 for allowing cooling medium (cooling water or cooling oil) to
flow outside the cavity 14 (at a position corresponding to the
periphery of the outer surface of the dome cover 6).
[0059] A gate pin member 18 is removably inserted into the gate
port 16. The gate pin member 18 is slidable in the vertical
direction between the pulled-out position shown in FIG. 1 and the
inserted-position shown in FIG. 2. As shown in FIG. 1, in a state
in which the gate pin member 18 is pulled to the pulled-out
position, the gate port 16 of the upper mold 12 is opened, and
hence injection of resin into the cavity 14 through the gate port
16 is enabled. On the other hand, as shown in FIG. 2, in a state in
which the gate pin member 18 is inserted to the inserted-position,
the gate port 16 of the upper mold 12 is closed by the gate pin
member 18, and a continuous surface is formed by an upper mold
inner peripheral surface 19 around the gate port 16 and a pin end
surface 20 of the gate pin member 18. In other words, as shown in
FIG. 2, the upper mold inner peripheral surface 19 around the gate
port 16 and the pin end surface 20 of the gate pin member 18 are
brought into a continuous state without a level difference.
[0060] Here, the upper mold 12 of the injection molding die 11 may
be considered to be an outer mold for molding the outside portion
of the dome cover 6, and corresponds to a first metal mold in the
present invention. The lower mold 13 of the injection molding die
11 may be considered to be an inner mold for molding the inside
portion of the dome cover 6, and corresponds to a second metal mold
of the present invention.
[0061] Referring now to FIG. 6 and FIG. 7, a configuration of an
ultrasonic welder apparatus 21 for applying a secondary processing
to the dome cover 6 will be described.
[0062] FIG. 6 and FIG. 7 show a state of applying the secondary
processing to the dome cover 6 manufactured by injection molding.
FIG. 6 is a side view showing a state of applying the secondary
processing to the zenithal portion 15 of the dome cover 6 and FIG.
7 is a perspective view showing a state of applying the secondary
processing to the zenithal portion 15 of the dome cover 6.
[0063] As shown in FIG. 6 and FIG. 7, the ultrasonic welder
apparatus 21 is used as the secondary processing apparatus for
applying the secondary processing to the zenithal portion 15 of the
dome cover 6 in this embodiment. The ultrasonic welder apparatus 21
includes an apparatus body, not shown, an ultrasonic transducer
provided in the apparatus body for generating ultrasonic
vibrations, and a horn member 22 to which the ultrasonic vibrations
generated by the ultrasonic transducer is transmitted. In this
embodiment, the horn member 22 of the ultrasonic welder apparatus
21 is configured to be vibrated in the horizontal direction
(lateral direction in FIG. 6) along a tangential direction (a
direction of a tangent line) at the zenithal portion 15 of the dome
cover 6.
[0064] The horn member 22 of the ultrasonic welder apparatus 21 has
a distal projection 23 in a projected shape. A lower surface 24 of
the distal projection 23 of the horn member 22 has a spherical
shape (recessed spherical shape) extending along the spherical
shape (projected spherical shape) of the upper surface of the
zenithal portion 15 of the dome cover 6. The lower surface 24 of
the distal projection 23 of the horn member 22 is applied with a
mirror finishing. Here, the ultrasonic welder apparatus 21
corresponds to the secondary processing apparatus in the present
invention, and the lower surface 24 of the distal projection 23 of
the horn member 22 corresponds to a contact surface in the present
invention.
[0065] Referring now to FIG. 1 to FIG. 7, a method of manufacturing
the dome cover 6 using the injection molding die 11 and the
ultrasonic welder apparatus 21 configured as described above will
be described.
[0066] When manufacturing the dome cover 6 in the embodiment of the
present invention by injection molding, as shown in FIG. 1, the
upper mold 12 and the lower mold 13 of the injection molding die 11
are closed to form the cavity 14 between the upper mold 12 and the
lower mold 13. Then, the gate pin member 18 is pulled out to the
pulled-position to open the gate port 16. Then, melted resin is
injected into the cavity 14 through the gate port 16. At this time,
the resin injected through the gate port 16 flows from the center
portion of the cavity 14 (the portion of the dome cover 6
corresponding to the zenithal portion 15) uniformly and
isotropically toward the circumference of the cavity 14.
[0067] As shown in FIG. 2, the gate pin member 18 is inserted to
the inserted-position to close the gate port 16 with the gate pin
member 18. When the resin in the cavity 14 is cooled sufficiently
and cured, the upper mold 12 and the lower mold 13 are opened and
the dome cover 6 which is a molded product is taken out from the
injection molding die 11 (see FIG. 3 and FIG. 4).
[0068] Subsequently, when applying the secondary processing to the
zenithal portion 15 of the dome cover 6, as shown in FIG. 6 and
FIG. 7, the lower surface 24 of the distal projection 23 of the
horn member 22 of the ultrasonic welder apparatus 21 is pressed
against the zenithal portion 15 of the dome cover 6.
[0069] Then, as shown by arrows in FIG. 6 and FIG. 7, the horn
member 22 of the ultrasonic welder apparatus 21 is vibrated in the
horizontal direction (the horizontal direction in FIG. 6) to melt
the resin at the zenithal portion 15 of the dome cover 6 again.
Then, the mirror-like shape of the lower surface 24 of the distal
projection 23 of the pressed horn member 22 is transferred to the
zenithal portion 15 of the dome cover 6. Then, generation of
ultrasonic vibrations from the ultrasonic welder apparatus 21 is
stopped, and the resin at the zenithal portion 15 of the dome cover
6 is cured again.
[0070] In this manner, the secondary processing is applied to the
zenithal portion 15 of the dome cover 6. With such secondary
processing, if a gate trace 25 is formed at the zenithal portion 15
of the dome cover 6, the gate trace 25 may be shaded out.
[0071] By using the method of manufacturing the dome cover 6
according to this embodiment as described thus far, for example, a
dome cover 6 with thin zenithal portion 15 as shown in FIG. 8 is
manufactured easily. According to the dome cover 6 exemplified in
FIG. 8, the center of the inner semi-sphere of the dome portion is
offset toward the zenithal portion of the dome portion 9 with
respect to the center of the semi-sphere of the outside of the dome
portion 9. Accordingly, the dome thickness of the zenithal portion
15 of the dome portion 9 (the thickness in the direction vertical
to the dome surface) is thinner than the thickness of the dome in
the horizontal direction (the thickness of the periphery of the
dome portion 9). Accordingly, the optical path difference of the
dome portion 9 is reduced and, consequently, the aberration caused
by the optical path difference is reduced, thereby improving the
image quality of the camera image.
[0072] When the dome cover 6 shown in FIG. 8 is manufactured with
the manufacturing method of the prior art, since the cavity is
narrowed at the zenithal portion of the cavity, when the resin is
injected from a position corresponding to the flange portion of the
dome cover (the gate port on the lateral side of the cavity), the
injected resin may not flow into the zenithal portion of the
cavity, and hence the defective molding may occur at the zenithal
portion of the cavity. In contrast, with the manufacturing method
in this embodiment, since the resin is injected through the gate
port 16 positioned at the zenithal portion 15 of the dome cover 6,
the injected resin flows smoothly in the cavity 14, and hence
occurrence of the defective molding at the zenithal portion 15 of
the dome cover 6 is prevented. When the resin is injected through
the gate port 16 positioned at the zenithal portion 15 of the dome
cover 6, the gate trace 25 may be formed at the zenithal portion 15
of the dome cover 6. However, with the manufacturing method in this
embodiment, the gate trace 25 can be shaded out by applying the
secondary processing to the zenithal portion 15 of the dome cover
6. Therefore, the method of manufacturing the dome cover 6 in this
embodiment is optimal for manufacturing the dome cover 6 having the
thin zenithal portion 15 as shown in FIG. 8.
[0073] Evaluations of optical performance of the dome cover 6
manufactured in the manner as described thus far were carried out.
The evaluation of the optical performance of the dome cover 6 will
be described with FIG. 9 and FIG. 10.
[0074] First of all, an evaluation of the quality of a camera image
shot at the TELE end (the maximum telescopic focal distance of the
lens 5) with the lens 5 of the surveillance camera 4 directed in
the horizontal direction as shown in FIG. 9 was carried out. Here,
a dome cover in the prior art was used as a comparative example.
The dome cover 6 in this embodiment was formed by injection molding
by injecting resin through the gate port 16 positioned at the
zenithal portion 15 of the dome cover 6. In contrast, the dome
cover in the comparative example was formed by injection molding by
injecting resin from a position corresponding to the flange portion
of the dome cover, that is, the gate port on the lateral side of
the cavity.
[0075] Consequently, in a case in which the camera image was shot
with the lens 5 directed in the horizontal direction with the dome
cover in the comparative example (the dome cover in the prior art),
when the lens 5 is directed toward the gate port or the exit
portion on the flange portion, characters shot through the dome
portion were blurred to an unreadable state and lowering of the
image quality was recognized. In contrast, with the dome cover 6 in
this embodiment, the blur of the shot characters was reduced to a
readable level irrespective of the direction of the lens 5 in the
horizontal direction and improvement of the image quality was
recognized. It seems to be because of an effect such that the resin
injected from the center portion of the cavity 14 (the portion of
the dome cover 6 corresponding to the zenithal portion 15) flows
uniformly toward the circumference of the cavity 14 in the dome
cover 6 in this embodiment, and variations in pressure or
temperature of the resin in the cavity 14 are restrained, whereby
the molding irregularity of the manufactured dome cover 6 was
restrained.
[0076] Subsequently, an evaluation was carried out on the gate
trace 25 to check whether it was visible (eye-catching) or not with
a camera image shot through the lens 5 of the surveillance camera 4
at the WIDE end (the widest focal distance of the lens 5) directed
right downward (toward the zenith of the dome cover 6) as shown in
FIG. 10. In the comparative example, the dome cover which resin was
injected through the gate port 16 positioned at the zenithal
portion 15 of the dome cover 6 as in this embodiment but the
secondary processing was not carried out was used.
[0077] As a result, with the dome cover in the comparative example
(the dome cover without the secondary processing), a portion of the
gate trace 25 at the zenithal portion 15 of the dome cover 6 was
not transparent, so that the other side of the gate trace 25 could
not see through. In contrast, in the case of the dome cover 6 in
this embodiment, the gate trace 25 at the zenithal portion 15 of
the dome cover 6 was shaded out and the other side of the gate
trace 25 could see through. From this result, an effect that the
gate trace 25 is faded out by applying the secondary processing on
the zenithal portion 15 of the dome cover 6 was recognized.
[0078] According to the method of manufacturing the dome cover 6 in
the embodiment of the invention, by injecting melted resin into the
cavity 14 through the gate port 16 provided at the position
corresponding to the zenithal portion 15 of the dome cover 6, it
can be restrained to generate partial molding irregularity on the
manufactured dome cover 6.
[0079] In other words, in this embodiment, the resin injected from
the center portion of the cavity 14 (the portion corresponding to
the zenithal portion 15 of the dome cover 6) flows uniformly toward
the circumference of the cavity 14. Namely, the resin injected from
the center point of the cavity 14 being symmetric with respect to a
point flows isotropically (point-symmetrically) toward the portions
of the cavity 14 being symmetric with respect to a point.
Therefore, occurrence of variations in pressure or temperature of
resin in the interior of the cavity 14 can be restrained, and
generation of molding irregularity on the manufactured dome cover 6
can be restrained.
[0080] In this embodiment, application of the secondary processing
to the zenithal portion 15 of the dome cover 6 is achieved by
transferring the shape of the mirror-finished contact surface of
the secondary processing apparatus to the zenithal portion 15 of
the dome cover 6. For example, when the trace of the gate port 16
(gate trace 25) remains on the zenithal portion 15 of the dome
cover 6, the gate trace 25 can be shaded out easily by the
secondary processing by transferring. For example, the secondary
processing by transferring is performed by automating the secondary
processing processes with a machine, and hence a high productivity
of the dome cover 6 is ensured in comparison with the case of
shading out the gate trace 25 of the zenithal portion 15 of the
dome cover 6 by the secondary processing by hand polishing.
[0081] In this embodiment, the resin on the surface of the zenithal
portion 15 of the dome cover 6 is melted while being applied with
the ultrasonic vibrations. Therefore, complex temperature control
is not necessary and the degree of melt of the resin can be easily
controlled in comparison with the case in which resin is heated and
melted. When the vibrations caused by the ultrasonic waves are
stopped, the resin at the zenithal portion 15 of the dome cover 6
is cooled and cured. Therefore, the time required for curing the
resin can be shortened, and hence the time required for the
secondary processing can be reduced. For example, when the resin is
melted by the ultrasonic vibrations, the time required for melting
and curing the resin is on the order of 0.1 seconds. Thus, the time
required for the secondary processing can be significantly reduced,
and high mass-productivity of the dome cover 6 and the cost down of
the dome cover 6 are achieved.
[0082] In this embodiment, the contact surface of the secondary
processing apparatus is vibrated along the tangential direction at
the zenithal portion 15 of the dome cover 6. Accordingly, the resin
at the zenithal portion 15 of the dome cover 6 is easily melted by
friction generated between the ultrasonically vibrating contact
surface and the zenithal portion 15 of the dome cover 6. In this
case, since the direction of vibrations of the contact surface is
the tangential direction at the zenithal portion 15 of the dome
cover 6, the vibration energy generated by the ultrasonic wave can
be efficiently converted into friction energy in comparison with
the case of vibrating in the direction of a normal line of the
zenithal portion 15 of the dome cover 6.
[0083] In this embodiment, after the resin has injected, the gate
port 16 positioned at the zenithal portion 15 of the dome cover 6
is closed by the gate pin member 18, and the continuous surface is
formed by the upper mold inner peripheral surface 19 and the pin
end surface 20. Therefore, the gate trace 25 at the zenithal
portion 15 of the dome cover 6 can become smaller. In a case in
which the gate port 16 is not closed by the gate pin member 18, a
column shaped large gate trace 25 may be formed at the zenithal
portion 15 of the dome cover 6 with resin remaining in the interior
of the gate port 16. In contrast, in this embodiment, the gate
trace 25 at the zenithal portion 15 of the dome cover 6 is a small
gate trace 25 formed of a circular parting line between the gate
port 16 and the gate pin member 18.
[0084] Although the embodiment of the present invention has been
described by an example, the scope of the present invention is not
limited thereto, and modifications and alterations may be made
according to the object without departing the scope stated in
claims.
[0085] For example, the description is given about an example in
which the ultrasonic welder apparatus 21 is used as the secondary
processing apparatus, and the horn member 22 is ultrasonically
vibrated to melt the resin at the zenithal portion 15 of the dome
cover 6. However, the scope of the present invention is not limited
thereto. For example, the resin at the zenithal portion 15 of the
dome cover 6 may be heated and melted.
[0086] The preferred embodiment of the present invention which is
conceivable at the present moment has been described thus far.
However, the fact that various modifications may be made with
respect to this embodiment is understood and the fact that such
modifications within the sprit and scope of the present invention
are included in the appended claims is intended.
INDUSTRIAL APPLICABILITY
[0087] As described above, the method of manufacturing the dome
cover according to the present invention has an effect such that
generation of partial molding irregularity on the manufactured dome
cover is restrained, and is effective as a method of manufacturing
dome covers used for dome-type surveillance cameras.
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